Velocity measuring device



y 9 w. VAN B. ROBERTS 2,157.572

VELOCITY MEASURING DEVICE Original Filed Feb. 25, 1933 AMPLIFIER Ala. 2

INVENTOR WALTER VAN B. BERTS BY M ATTORNEY Patented May 9, 1939 UNITED STATES VELOCITY MEASURING DEVICE Walter van B. Roberts, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Original application February 25, 1933, Serial No.

658,654, now Patent No. 2,102,166, dated December 14, 1937.

Divided and this application I June 8, 1.937, Serial No. 147,062

3 Claims.

The present application is a division of my copending application Serial No. 658,654, filed -February 25, 1933, entitled Velocity measuring devices 'now U. S. Patent No. 2,102,166 dated 5 December 14, 1937.

This invention relates to a device for measuring the speed of a golf ball, especially for the precise comparison of speeds attained by successive strokes. The object of such a device is to provide a means for instructing players in a convincing fashion as to what sort of stroke will produce the highest ball speed which in turn means the longest drive, other things being equal. It is an object of the present invention to provide a mechanism for use by the professional in connection with his teaching work which will enable him to demonstrate to the pupil that the properly executed and relatively eliortless stroke actually produces a greater ball speed than 20 strokes involving great conscious exertion even when the ball is squarely hit with one of. these strokes. Of course, it is possible for a golfer to come to the same conclusions as a result of driving a large number of balls from the tee, but

in this case it is diflicult to tell which of the balls really starts the fastest as the distance travelled depends considerably upon the nature of the soil where the ball hits and the trajectory etc. so that only-by observing the average results of a 80 number of strokes can any conclusions be reached. In contrast to this the present invention requires only a single well hit shot to establish a value of ball speed which can be obtained with a proper stroke and then the player need only make one Well hit shot involving great conscious efiort to demonstrate that no greater speed can be attained.

It is an object of the present invention to produce a mechanism which will be fully automatic {0 to indicate visually a reading indicative of the ball speed and retaining the reading for as great a length of time as desired, the reading being erased before the next operation of the apparatus by a manually controlled button.

duce a mechanism which will be fully automatic in that a number of strokes may be made in rapid succession without any attention or adjustment to the recording means, the speed of the ball at each stroke being indicated for sufficient length of time to be observed, the indication, however, not occurring until two or three seconds after the ball is struck so as to allow the stroke to be completed at leisure before the 'at- 56 tention is transferred to the indicating means,

It is another object of the invention to proafter which the entire mechanism of its own accord reverts to its original condition and is ready to indicate the speed of the next ball struck without any adjustment or resetting of any of its parts. Preferably,'the device of this invention is to be used in connection with one of the automatic teeing machines at present on the market, which include a hopper to hold a large number of balls and a trigger arrangement, the actuation of which, releases one ball and allows it to roll out of the machine and into position on a rubber tee of suitable height for driving. With this preferred combination the pupil may strike ball after ball with the minimum ofinterruption between shots and thus retain in his mind the feel of each stroke together with the resulting ball speed and hence rapidly learn the proper feel for the best results.

In the drawing,

Fig. 1 illustrates schematically one embodiment of the present invention utilizing thyratrons to control the charging of a condenser arrangement;

Fig. 2 illustrates another modification of the invention which is entirely automatic; and,

. Fig. 3 is another modification of the invention wherein the circuits are somewhat simplified.

Referring particularly to Fig. 1 there is shown a player I about to drive off. As pictured, the player is about to swing his club 3 and hit the teed ball 2 against the screen 20, the path of the ball is shown by the dotted lines. A microphone 4 connected to the usual microphone circuit comprising a source of current 5 and the primary of an audio transformer 6, is located adjacent the teed ball 2. The microphone is preferably provided with a reflector which concentrates sound from the impact between the club and the ball at the microphone. A similar microphone l'l connected to the usual microphone circuit comprising current source 22 and primary of transformer 23 is located preferably directly behind the screen 20. A pair of thyra tron tubes 8 and it having input and output circuits are arranged 50 as to be respectively af- 1 fected by the microphones 4 and H. The input circuit of thyratron 8 comprises a variable bias ing source 1 and the secondary --of transformer 6 while the input circuit of thyratron i3 ineludes variable biasing source 2| and the secendary of transformer 23. The output circuits of both the thyratrons include a common portion comprising anode current source 9, switch 21, resistances I0 and i9 and solenoid ll. Sole noid H is arranged to operate a switch I2, the

,closure of which completes a circuit comprising condenser l3, current source l5 and resistance I6. An electrostatic voltmeter I4 is shunted across condenser l3 for giving an indication of the charge on the condenser. A condenser discharging circuit is provided which includes the normally open switch 26 and resistance 24. A spring controlled push-button 25 is arranged to cooperate with switches 21 and 26. Depressing the push-button opens switch 21 and closes switch 26 for purposes to be hereinafter pointed out.

The operation of the system shown in Fig. 1 is as follows:

Microphone 4 which, as previously stated, is located preferably close to the ball 2, responds to the sound emitted when the club 3 comes in contact with the ball. The sudden change in microphone current will (if the polarity of the transformer 6 is correct) kick the grid of the thyrat'on 8 in a positive direction and thus start current in this thyraton. Part of this current flows through solenoid H and thus closes contact |2 allowing condenser 3 to charge through resistance "5. About a 20th of a second later the sound of the ball 2 hitting the screen 20 similarly starts fthyratron" l8 and thus neutralizes the current inthe solenoid II and switch |2 opens by means of gravity or a suitable spring. (If the relay is polarized the second thyratron current can be arranged to have a greater effect than the first so that the magnet pull reverses in direction when the second thyratron" starts.) Resistance l6 times capacity I3 is chosen so as to have a time constant which is approximately equal to of a second so that the voltage to which I3 is charged will be approximately proportional to the time of flight of the ball and is indicated by electrostatic voltmeter i4. After the reading of l4 has been noted the machine is restored to its original condition by pressing-button 25 which discharges condenser l3 in a nonoscillatory fashion through resistance 24 and also breaks the plate circuits of the two "thyratrons 6 and I6 so as to stop the "thyratron currents. another drive.v It should be understood that if necessary suitable amplifiers may be provided between the two microphone output circuits and the associated "thyratron" inputcircuits.

In Fig. 2, the system up to the transformers 6 and 23 is the same as described above in connection with Fig. 1. The secondary of the transformer 6 forms part of the input circuit of an amplifier 29 which is identified as amplifier No. 1. The output of the amplifier 29 includes the primary oftransformer 36, the secondary of which forms part of the input circuit of the tubes 35 and 31. These two tubs are connected with their respective circuits arranged so as to form a push-pull rectifier arrangement wherein grid condensers 33 and 32 are provided in combination with the respective leak resistors 34 and 38, the output of the devices 35 and 31 includes the source of space current 36 and -the coil of a solenoid 39.

- The output of the microphone I1 is transferred to the input of amplifier 26 which is characterized in the drawing as amplifier No. 2. The output of amplifier 26 is coupled to the input of a second push-pull detector arrangement through the transformer 3|. This second push-pull detector arrangement comprises a pair of tubes 53, 54 with their respective .grid condensers 56 and The system is then in condition for 51 and leak resistors 55 and 56 respectively. The common output circuit of the tubes 53 and 54 comprises a source of space current 52 and the coil of a solenoid 41. Solenoid 39 which is in the output of the first push-pull detector circuit is arranged so as to operate the spring control switch 5|, the latter is adapted to cooperate either with"a stop 40 or a contact clip 4|. The solenoid 41 is arranged so as to controlthe switch blade 50 which in turn is .provided with a spring 46. Cooperating with the blade 59 are two contacts 49 and 48. A connection is provided between the switch blade 50 and contact 4| which includes a resistance 45 and a condenser 44 in series. A conductive connection is provided between the contact 48 and contact 4|. Between the contact 49 and the switch blade 5| are connected in series a source of current 42 and a ballistic galvanometer 43.

The operation of the system shown in Fig. 2 is as follows:

Sound arriving at the microphone 4 due to the impact of the club 3 on the ball 2 is amplified if necessary by means of the amplifier 29, the output of which is impressed upon the push-pull rectifier tubes 35 and 31. The values of the grid condensers 33 and 32 and the leak resistors 34 and 36 are so chosen that immediately upon voltage being impressed upon the input of the two rectifier tubes the grid potential becomes negative and remains negative for an interval of time 'of the order of magnitude of a 10th of a second,

whereby the current through the winding of condenser 44, contact 4|, armature 5| and the battery 42.

About a twentieth of a second after the ball has been struck, however, it hits a screen 26 and the resulting sound is picked up by microphone 1, amplified if necessary by amplifier 28 and impressed upon the input circuit of the push-pull pair of rectifiers 53, 54. Grid condensers 51, 56 and leak resistors 56, 55 have values such that a current through solenoid 41 will remain abnormally small for a period of considerably more than a tenth of a second say in the order of several seconds. As soon as the current through 41 is diminished, spring 46 pulls armature 56 away from contact 49 and over against contact 46. By pulling this armature away from contact 49 the circuit through the galvanometer 43 is opened and thus current has only been allowed to flow through the galvanometer during the interval between the striking of the ball 2 and the ball striking the screen 26, although it is not essential that this interval be exactly the same as the time of flight which is determined by the length of time during which the circuit is complete, will not reach its maximum value until 2 or 3 seconds after the ball has been struck. It will be noted that the contact of armature 56 against point 46 discharges condenser I4 and thus prepares the condenser for the next cycle of operation. As described previously, the armature 5| will fall back into its normal open circuit position before the armature 50 falls back into its normal position so that there will be no secondary charging of condenser 44. Thus, stroke after stroke may be played within a few seconds of each other without any attention to the mechanism.

Figure 3 shows a somewhat simplified modification of the device of Figure 2. The difierence in this case consists in using a single rectifier tube in combination with each microphone and con"- necting a single relay winding differentially to the plates of these two tubes each of which is fed with direct current through a high impedance.

In Figure 3, the system shown is similar to the system of Figure 2 up to and including the transformers 30 and 3i. The output of amplifier 28 feeds into the input of rectifier tube 63 through the coupling transformer 3|. The input of tube 83 includes the grid condenser 59 and the leak resistor 62. The output of amplifier 29 feeds into the input of rectifier tube 64 through the coupling transformer 30. The input of tube 64 comprises grid condenser 60 and leak resistor 6|. Tubes 63 and 64 are arranged so as to have a common output circuit which comprises a source of space current 16, resistors 55 and B6 and solenoid 69 the latter being energized by the plate currents. Solenoid 69 is adapted to control a movable switch blade I5, said switch blade is normally adapted to cooperate with a contact 61 through the pull of spring III. A second contact 5! is provided to cooperate with the blade 15 when the solenoid 69 is energized. The two contacts 51 and 68 are connected to each other through a galvanometer 'H and a source 01' current 12 in series while the blade I5 is permanently connected to one side of the source 12 through a series arrangement of condenser 13 and resistance 14.

The system shown in Fig. 3 operates as follows:

The relay armature I5 is normally held against point 51 by means of spring 10. When the impulse arrives from amplifier 29 the balance of the two rectifiers is upset and current flows through winding of 69 in such direction as to pull armature 15 over against contact 58 thus starting current to fiow through galvanometer 1 I. When the impulse from amplifier 28 arrives, however, the current through winding 59 is neutralized or reversed in direction thus allowing armature 15 to be pulled back against point 81 thus interrupting the galvanometer circuit at the end of the proper interval and also discharging condenser 13.

It should be understood that the systems disclosed herein and those falling fairly within the scope of the appended claims are not limited to indicating the speed of golf balls and the like but also include the determination of the speed of any moving body, or the measurement of any time intervals oi suitable order of magnitude whose limits are capable of being indicated by electrical impulses.

I claim:

1. A short interval timer comprising a first and second control energy pickup means, a capacitor, a charging circuit for the capacitor including a source of current, a pair of electronic tubes having separate input circuits and a common output circuit, said common output circuit including a relay for connecting the charging circuit to the capacitor, means including a connection between said first pickup means and one of said input circuits for operating said relay means to connect the charging circuit to said capacitor to initiate the charging of said capacitor by said source upon the interception of control energy by the first pickup means, means including a connection between the second pickup means and the other of the input circuits for operating said relay means to terminate the charging of the capacitor upon the interception of control energy by the second pickup means, means for indicating the total charge received by the capacitor and means for discharging the capacitor.

2. A short interval timer comprising a first and second sound energy pickup means, a capacitor, a source of charging current therefor, a pair of electronic tubes having separate input circuits and a common output circuit, said common output circuit including a relay for connecting the source of charging current to the capacitor, means including a connection between said first pickup means and one of said input circuits for operating said relay means to initiate the charging of said capacitor from said source upon the interception of sound energy by said first pickup means, means including a connection between the second pickup means and the other of said input circuits for operating said relay means to terminate the chargin of said capacitor upon the interception of sound energy by the second pickup means, means for indicating the total charge received by the capacitor and operable means acting upon operation to disable both of said electronic tubes to thereby prevent energization of said relay thereby and to discharge the capacitor.

3. A short interval timer comprising a first and second control energy pickup means, a capacitor, a' charging circuit including a source of current for the capacitor, 9. pair of grid controlled gaseous discharge tubes of the type wherein the voltage on the grid controls the starting of plate current which once set up cannot be further influenced by the grid under normal operating conditions but may be stopped by reducing the anode potential below the ionization potential ofthe gas in the tube, said tubes being provided with separate input circuits and a common output circuit, the common output circuit including a relay for connecting the charging circuit to the capacitor, means comprising a connection between said first pickup means and one of the said input circuits for starting the flow of plate current in said tube to cause operation of said relay means to initiate the charging of said capacitor upon the interception of sound energy by said first pickup means, means comprising a connection between the second pickup means and the other of said input circuits for starting the flow of current through the other of said tubes and hence through the relay means to buck out the other energizing current in the relay means and thereby disconnect the charging circuit from the capacitor upon interception of sound energy by the second pickup means, means for indicating the total charge received by the capacitor and means for reducing the plate potential applied to the two tubes below the ionization potential of the gas in said tubes and thereby stop the flow of current through both of the tubes and at the same time discharge said condenser.

' WALTER vm B. ROBERTS. 

